The inactivity alert on the Leaf will require you to make a certain number of steps in the time period that you have chosen in the app’s Settings. The exact number of steps that you need to make depends on your usual activity levels and it will differ for everyone. So if the Leaf vibrates, even though you have just been moving, it might be possible that you simply haven’t made enough steps and your Leaf is simply nudging you to be even more active.